Collagen is the most abundant protein in vertebrates. It consists of three polypeptide chains that form an extended right-handed triple helix. Each polypeptide chain is composed of approximately 300 repeats of the sequence X-Y-Gly, where X is often a proline reside and Y is often proline or hydroxyproline residue. The gamma-substituted derivatives hydroxyproline and fluoroproline act to stabilize collagen. The purpose of this investigation is to use NMR to analyze the mechanisms by which the gamma-substituents effect on proline rings' conformation and configuration and therefore on the stability of colagen-like peptides. Homonuclear and heteronuclear vicinal spin-spin couplings in N-acetylproline methylester, N-acetyl-(S)-hydroxyproline methylester, and N-acetyl-4(S)-fluoroproline methylester will be obtained at temperatures ranging from 4?C to 43?C in 4?C intervals. The continuous probability distribution (CUPID) method will be applied to the coupling constants at each temperature for each proline derivative to determine ring pucker temerature profiles for both cis and trans configurations. The configurational analysis (determining the cis/trans ratio) for the varying temperatures and proline derivatives will also be determined by comparison of peak volumes for the cis and trans conformations. The results are expected to give new insights into the mechanism of collagen stabilization by -OH and -F substituents in the gamma-position of proline rings.